1. Field of the Invention
The present invention relates to a vacuum envelope and an electron emission display using the vacuum envelope, and more particularly, to spacers disposed in the vacuum envelope to provide a supporting force to the vacuum envelope against an external force.
2. Description of Related Art
A conventional electron emission display includes an array of electron emission elements disposed on a first substrate and a light emission unit disposed on a second substrate. The light emission unit includes phosphor layers and an anode electrode.
The first and the second substrates are sealed together at their peripheries using a side member, and an inner space between the substrates is exhausted to form a vacuum envelope such that an emission and a migration of electrons can occur smoothly therein.
A plurality of spacers are mounted in the vacuum envelope to counter a compression force generated by a pressure difference between an interior and an exterior of the vacuum envelope.
The spacers can be classified into first spacers arranged in an active area of the vacuum envelope and second spacers arranged in a non-active area of the vacuum envelope. The active area is for displaying an image, and the non-active area is not for displaying an image. In general, the first spacers are positioned to correspond to a black layer disposed between the phosphor layers, and the second spacers are arranged along an outer circumference of the active area between the first and second substrates.
According to a conventional process for manufacturing the electron emission display, the first spacers are disposed on the active area of the vacuum envelope at the first substrate, and the second spacers are disposed on the outer circumference of the active area. Then, a side member is disposed on an edge of the first substrate. The second substrate (on which the phosphor layers, the black layer and the anode electrode are disposed) is then attached on the first substrate. Next, the inner space defined between the first and second substrates is exhausted. The manufacture of the electron emission display is thereby completed.
The compression force applied to the first and second substrates of the vacuum envelope increases gradually from outer portions of the substrates to central portions of the substrates. Therefore, the first and second substrates may be caused to have a concave shape at their central portions. That is, the central portions of the substrates may be caused to round inwardly towards the interior of the vacuum envelope such that each of the substrates has a shape of a concave lens.
As a result, a distance between the first and second substrates at an outermost portion of the active area may be greater than a distance between the first and second substrates at other portions of the vacuum envelope. Therefore, the first spacers disposed near the outermost portion of the active area may be in an unstable contact with the black layer. The unstable contact of the first spacers with the black layer distorts electron beams emitted in a vicinity of the unstable contact. A quality of light emission is thereby deteriorated.